This application claims the benefit of Korean Application No. 2001-10739, filed Mar. 2, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a micromirror device for driving a micromirror to change a path of reflection of an incident light, and more particularly to a micromirror device in which a micromirror tilts with respect to a plurality of rotation axes so that the micromirror can function as a color switch, and to a projector employing the micromirror device.
2. Description of the Related Art
In general, a micromirror device includes a plurality of micromirrors driven by electrostatic forces. The micromirror device changes a path of reflection of incident light by changing an angle of reflection according to the tilt angle or tilt direction of each micromirror. The micromirror device is used in an image display device of a projection television and an optical scanning apparatus of scanners, photocopiers, and facsimiles. In particular, when the micromirror device is adopted in an image display device, the micromirror device includes as many micromirrors as a number of pixels of the image display device, where the micromirrors are arranged in two dimensions. When generating an image, the angle of reflection of incident light is determined by independently driving each micromirror according to a video signal and with respect to each pixel.
Referring to FIG. 1, a conventional micromirror device 5 includes a substrate 10, an address electrode 11, and a landing electrode 12 formed on the substrate 10. A pair of posts 15 supports a micromirror 16 and a torsion hinge 14 is connected between the micromirror 16 and each post 15 for receiving torsion when the micromirror 16 tilts. A voltage is applied to the landing electrode 12 to control the tilt angle or tilt direction of the micromirror 16. Here, the micromirror 16 is driven by electrostatic attraction generated by a difference in electric potential between the address electrode 11 and the micromirror 16.
FIG. 2 shows a projector employing the conventional micromirror device. In particular, a light source 20 emits a beam, which is condensed by a first condenser 22 and input to a color wheel 25. Here, the color wheel 25 is rotated at a high speed to realize color using the micromirror 16 of FIG. 1 (not shown), so that a color image is realized in a manner in which a light of R (red), G (green) and B (blue) colors sequentially illuminates the micromirror 16. The beam passing through the color wheel 25 is input to a DMD (digital micromirror device) chip 30 where the micromirror devices 5 of FIG. 1 (not shown) corresponding to a number of pixels of a screen 35 are arranged via a second condenser 27. When each of the micromirrors 16 tilts at a predetermined angle driven by the DMD chip 30 according to a video signal with respect to each pixel of the screen 35, a color beam corresponding to each pixel is reflected at an appropriate angle and proceeds towards a projection lens 33. A beam enlarged by the projection lens 33 is focused on the screen 35.
In this case, because the color wheel 25 rotates at high speed, noise is generated and stability is deteriorated due to the mechanical motion of the color wheel 25. Also, light is lost at a boundary portion of the color wheel 25. To reduce the loss of light, light should be focused to have a very small beam size. However, because the light source 20 is not a point light source and has a certain volume, there is a limit in reducing the size of the beam and, thus, the loss of light is unavoidable. Furthermore, because the unit price of the color wheel is very high, the total cost of manufacturing increases.
Various objects and advantages of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To solve the above and other problems, it is an object of the present invention to provide a micromirror device in which a micromirror tilts with respect to a plurality of rotation axes so as to function as a color switch, and a projector employing the micromirror device.
Accordingly, to achieve the above and other objects, there is provided a micromirror device for driving a micromirror, which includes a substrate; electrodes on the substrate; first posts; and a support frame supported by the first posts and tilting with respect to rotation axes using portions supported by each of the first posts as hinge points.
In the present invention, the electrodes are symmetrically arranged in pairs on opposite sides of the substrate, each pair of electrodes facing each other. The micromirror tilts with respect to two rotation axes and the rotation axes are perpendicular to each other.
The support frame includes a second post protruding from the support frame supporting the micromirror; a center portion supporting the second post; and two pairs of springs connecting the first posts with the center portion. The two pairs of springs are arranged to be symmetrical with respect to each other and have zigzag shapes to be twisted and elastically deformed when the micromirror tilts.
Also, to achieve the above and other objects, there is provided a projector including a light source emitting a light beam; a light beam splitting unit splitting the light beam from the light source according to a wavelength region of the light beam and transmitting and/or reflecting the light beam split at different angles; micromirrors; micromirror devices forming an image by independently pivoting each of the micromirrors in a predetermined direction and angle and controlling the micromirrors to selectively reflect the light beam, each of the micromirrors tilting with respect to rotation axes; a screen; and a projection lens unit magnifying and transmitting an incident light beam from the micromirror devices to proceed to the screen to form the image.
In the present invention, that each of the micromirror devices includes: a substrate; electrodes on the substrate; first posts; a support frame supported by the first posts and tilting with respect to the rotation axes using portions supported by each of the first posts as hinge points; a second post protruding from the support frame; and a micromirror supported by the second post and tilting by interaction with the electrodes.
Also, to achieve the above and other objects, there is provided a micromirror device including: a substrate including a built-in SRAM: electrodes on the substrate to tilt the micromirror; at least three posts on the substrate; and a support frame supported by the posts, wherein the micromirror is tilted in four directions by interaction with the electrodes.
A micromirror device is also provided, including: a micromirror receiving a red light beam, a green light beam, and a blue light beam at different angles, and a projection lens unit selectively receiving and displaying each of the red, green, and blue light beams according to incident angles of each of the red, green, and blue light beams and a tilt angle of the micromirror corresponding to each of the incident angles to realize color.
A micromirror device for driving a micromirror is also provided, the micromirror device including: a substrate; electrodes on the substrate; and a support frame supported by tilting with respect to rotation axes, wherein the micromirror tilts in four directions by applying a voltage to any one of the electrodes; and a projection lens unit selectively displaying red, green, and blue colors according to a direction of tilt of the micromirror.
These together with other objects and advantages, which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.